Electric discharge devices



nited States lkatent ELECTRIC DISCHARGE DEVICES Richard M. Walker,Roxbury, Mass., assigner *to Microwave Associates, Inc., Burlington,Mass, a corpora- 'vtion of Massachusetts Application May 2, 1958, SerialNo. 732,720

22 Claims. (Cl. 315-39) The eld of the present invention is generally-that of electric discharge devices within wave guide sections whichconstitute .gas or vapor filled envelopes, and more `particularly oftubes for duplexing systems with `principal gap electrodes as well asauxiliary "keep alive electrodes.

In pulse radio direction and range finding equipment where a commonantenna is `essential to yaccurate loca- .tion 'of la target it is thefunction'of la duplexing system alternately to transmit the powerfulsignal from the magfnetron lto the antenna while protecting the highlysensitive crystal receiver from this signal pulse, and to pass thereturning echo pulse from the lantenna to the receiver. For that purposeso-called transmit-receive tubes (commonly referred to as TR tubes) areemployed as switching devices on the one hand to :short-circuit thetransmission line leading to the receiver in order to protect thecrystal during the high power pulse transmission, and on 'the other handto allow the low level echo signal from a target to reach `the receiverwith minimum attenuation,

TR tubes are therefore in essence switches actuated by the high powertransmitted pulse, and in the absence of this pulse they are matchedsections of transmission line.

Devices according vto the invention are particularly applicable togap-discharge TR tubes of which the herein described practicalembodiments are characteristic examples, whetherus'ed in pairs withvshort slot hybrids or yequivalent devices to form a radar subassemblyknown as a 'balanced duplexer, or used as so-'calledanti-transmitreceive tubes (commonly referred to as ATR tubes) to form asubassembly known `as a 'branched guide duplexer; in either case thepurpose is to provide maximum efiiciency of transmission and receptionin radar or similar equipment using a common antenna. However theydevices herein described are also applicable 'to filters, cavities andother wave guide devices.

The essential :desirable characteristics of a TR tube are 'lowattenuation of the transmit-ted pulse that is low arc loss, lowattenuation of the received echo signal that is low insertion loss, highpower handling, long life, short recovery time, and broad hand width. Inprevious designs the optimal conditions for any one of thesecharacteristics are not necessarily favorable for other characteristicsand therefore the overall design of discharge devices of this type hasnecessarily been a compromise between two or more of thecharacteristics.

Objects of the invention are to provide gap tuning elements and keepalive 'structures for devices of the above indicated type, preferably incombination but also vfor separate use, and particularly also incooperation with dual element input and output windows which are thesubject matter of the application Serial No. 657,585, tiled on May 7,1957, for the purpose of materially improving one or more oftheabove-mentioned characteristic properties without material detrimentaleffect on other characteristics: to provide a gap tuning element capableof barrier discharge occurs at a window; to provide a gapv tuningelement which favors broad band matching of ,the TR tube; to provide akeep alive structure which is particularly suitable for gap structures,of the above Iindicated type and which combines the favorablecharacteristics of the conventional keep alive arrangements whileavoiding their defects; to provide a keep alive structure which retainspermanently low leakage and low radio frequency noise; to provide a gapand keep alive structure which inherently prevents short circuiting andwhich removes the locus of gas discharge from the electromagnetic fieldin the transmission lines; to provide devices of the above type allcharacteristics of which are uniformly favorable, which lower the arc aswell as the insertion loss and which give considerably longer tube lifeas compared with conventional ldevices of this type; to provide a newdouble gap resonant tuning structure which has a greater Q range thanconventional devices of that type and which has an improved performancewhen the gaps are tired; to provide a TR tube construction which permitsthe use of two keep alives each acting independently on two gaps of adouble gap structure; and to provide such devices which are mechanicallysimple and can be manufactured with the requisite precision; andgenerally speaking to provide devices of this type which have Aanessentially improved practical design from the point of View ofreproducibility and iiexibility.

A brief summary of the invention will serve to indicate various aspectsof its nature and substance for accomplishing the above objects, asfollows.

In one lof its broader aspects, the invention employs within a waveguide section, transversely elongate eiectrode means having an outersurface region which extends between opposite wall portions of the guidesection and which forms a discharge gap or gaps with complementalelectrode means extending from a third wall por-tion toward the elongateelectrode means; the elongate electrode means can extend freely throughthe wave guide section, or can be near or embedded in a wall portion.The elongate transversely extending electrode can form discharge gapswith various types of complemental electrodes, such as conical or postelectrodes of conventional type, or other such as skew-wise extendingelongate electrodes. In an important practical embodiment of theinvention, the elongate electrode is placed between two pointedelectrodes such as truncated cones extending from opposite portions suchas the wider walls of a wave guide and with their common axisintersecting the axis of Vthe elongate electrode which extends betweenthe two other, narrower, wall portions of the guide section.

In another important aspect of the invention the elongate electrode ishollow having an exposed outer surface portion extending transverselybetween two opposite wall portions of the guide and having in thissurface portion a perforation transversely through a wall portion of thehollow body leading into the guide proper, and further comprisingmetallic rod means extending into the hollow body and terminating nearthe perforation, whereby the hollow body provides a gap electrode aspointed out above, whereas the rod means provides a keep alive devicefor a gap formed near the perforation. In an important practicalembodiment, the metallic rod means which forms the auxiliary keep aliveelectrode has the shape of a wire in the axis of the tubular principalelectrode within which it is appropriately supported and from which itextends towards the outside through a seal. In the aforementionedimportant practical embodiment with two gaps, the hollow principalelectrode has two diametrically opposite perforations facing the twopost electrodes and one or two auxiliary keep alive electrodes 'aremounted therewithin as mentioned above.

In gaseous gap discharge tubes of the duplex type wherein two guidesections are placed adjacent to each other, two wave guide walls, suchas two narrower walls can be placed near to or contacting each otherwith an elongate electrode penetrating both adjacent walls and extendinginto both wave guide sections; in an embodiment of this type theseelongate electrodes can be `tubular and contain keep alive electrodesterminating at perforations of the tubular main electrodes, and thisarrangement then provides a connection between the two wave guidesections such that the gas or vapor lling will always be identical.Electromagnetic inductances can be formed in such tubes by structuressuch as rods or baffle plates extending between the guide section wallsand the elongate electrodes.

Although the herein described embodiment uses a tubular principalelectrode in combination with a keep alive electrode therewithin asoutline above, it should be understood that the concepts of transverselyelongate principal electrodes and of keep alive arrangement therein canbe used independently. For example the elongate principal electrode canbe solid and used together with a conventional keep alive electrodewithin one or two of the post electrodes. Or a keep alive arrangementaccording to invention, for example one arrange-d near or 4within one ofthe wave guide walls can be used together with two conventional postelectrodes.

These and other objects and aspects of the invention will appear fromthe following description of several typical embodiments illustratingits novel characteristics.

The description refers to a drawing in which Fig. l is a longitudinalaxial section of a wave guide portion constituting a TR tubeincorporating the invention, with the post electrodes shown inelevation;

Fig. 2 is a section on lines 2 2 of Fig. l again with the postelectrodes shown in elevation;

Fig. 3 is a section similar to Fig. 2 but in larger scale and with twoauxiliary keepI alive electrodes;

Fig. 4 is a section on lines 4-4 of Fig. 3;

Fig. 5 is a longitudinal section similar to Fig. l, of an embodiment ofthe invention which has a tubular principal electrode in a wall sectionof the guide and a single post electrode;

Fig. 6 is a section on lines 6 6 of Fig. 5; and

Fig. 7 is a further embodiment with a solid elongate principal electrodeand an electromagnetic inductance device in the forrn of baille plates.

Figs. 1 and 2 indicate at 21 a wave guide section constituting atransmit-receive tube which, as well known is sealed at both ends withresonant coupling windows, highly evacuated and instead lled with gas ofexact predetermined composition and pressure. Numerals 22.1 and 22.2indicate two flanges of the wave guide section with the aid of which itcan be joined to other sections of the system. 23.1, 23.2 and 24.1 and24.2 are conical electrode posts which, while in themselves well knownin the art are components of the present invention as will be describedbelow. The two sealing windows or irises are indicated at 25.1 and 25.2,and these are constructed in accordance with the teachings of theabove-mentioned copending application Serial No. 657,585, iiled on May7, 1957. As described in that application, the windows according to oneof its embodiments comprise an iris component indicated at 26 and adielectric sealing component indicated at 23.

The principal electrodes 23.1 to 24.2 are of conventional design, withbushings 31, conically pointed and threaded electrode posts 32, and locknut means 33. It will be understood that the length of projection ofthese electrodes can be varied in any desirable manner including remotecontrol by means of mechanical or solenoid devices, as well known in theart. By means of such devices the gaps can be adjusted and the posts canalso be used as shutters for closing a desired wave guide com- Theelongate principal electrode according to the invention is indicated inFigs. l to 4 as consisting, in this embodiment, of a tubular body 41which is secured in the opposite wall portions 21.1 and 21.3 of theguide section 21, by means of a bushing v42 made of metal that issuitable for forming a seal in the manner to be described below.

Perforations 45.1, 45.2 (Figs. 3 and 4) are made transversely of thewalls of the tubular electrode 41, in alignment with apices of the twopost electrodes 23.2 and 24.2. An auxiliary keep alive electrodeassembly according to the invention comprises a wire 46 of suitablealloy held in place by a glass body 47 which has a supporting bead 47.1,an insulating coating 47 .2 and a sealing and insulating support 47.3from which protrudes the outer end 46.1 of the electrode wire, where itcan be connected to the keep alive voltage supply source. The inner end46.2 of the keep alive electrode wire is free from insulation andreaches practically towards the center line of the perforations 45 inthe manner to be elaborated below. it will now be evident that by meansof this construction two keep alive electrodes can be applied to onedouble gap as shown in Fig. 3, or that, as shown in Fig. 2, a tube withat least one perforation in each one of two adjacent wave guide sections21, 27, with adjacent wall portions 21.1, 27.1 can serve to establish apneumatic communication between the two sections.

A second keep alive device of identical construction is indicated at 48of Fig. 3.

Devices of this type require inductance for balancing the capacitance ofthe electrodes, and this can be provided by the rod system 51.1, 51.2,52.1, 52.2. Instead, as `will be described below, solid bafes can beused for the same purpose. in either case, the tubular electrode lendsitself well for mounting such inductances.

As previously mentioned, each one of the gaps, whose length is marked gin Fig. 4, can be separately adjusted if desirable, by provision such asindicated at 31, 32, 33 of Figs. 1 and 2.

Figs. 5 and 6 illustrate an embodiment with a single tubular electrodewhich extends transversely between the wave guide walls 21.11 and 21.31,being embedded in the longer guide wall 21.41. Otherwise it can have thesame construction as that described above with reference to Figs. l to3, especially the combination lwith a keep alive electrode by way of aperforation 55 opposite the apex of the electrode post 53. Fig. 6 alsoillustrates the use of two auxiliary electrodes 56 and 58 with thissingle gap device.

Fig. 7 shows a solid rod electrode 61 of the elongate type according to`the invention, in combination with two post electrodes 63, 64, each ofwhich is equipped with conventional keep alive electrodes 65, 66,respectively. This embodiment also illustrates the above mentioned useof solid ba'les as inductive balancing impedance.

ln an actual successfully operative embodiment according to Figs. 1 to4, the dimensions which are indicated in these figures were as follows.

The window construction of' this embodiment was that described in detailwith reference to Figs. 1 and 2 of the above identied patentapplication.

Characteristic electric data indicating the quality of this example areas follows.

Insertion loss db .5 Arc loss db .10 Bandwidth percent-- 15 Peak powerrating kw 500 Average power rating watts 500 Frequency kmo 9 antenas Theoperation of devices that incorporate this invention and the selectionof the configurations, mounting, combinations and dimensions of thevarious components for any given purpose is lgoverned by the followingconsiderations.

`'The vtuning elements in microwave circuitry incorporating theinvention are employed to provide small gaps where the electric eld 'ishigh thereby producing discharges at low power levels, to provide apreliminary `barrier to high level signals until the main discharge at`the window 'becomes effective, and to provide broad band matching ofthe tube sections of lthe wave guide.

The power level of the gap discharge which takes place when the -highsending energy begins to flowand which initiates high fields at theinput window that in their turn cause the finally leffective shuntingdischarge which lasts for the duration of the transmitted pulseisdetermined by the gap spacing g (Fig. 4) and the Q of the tuningelements. Reduction of the gap g decreases -the power level at which theinitial arc discharge takes place and decreases the leakage power of thetube. 'It was found vthat the new gap structure with an elongatevelectrode permits substantial reduction of the g dimension and hence ofthe power level at which the initial karc discharge takes place and thatit also Vdecreases the leakage power of the tube; furthermore itprovides a considerably greater range of Q as -compared to conventionaldesigns, and improves perfomance when the Igaps are fired.

Corning to the function of TH tube gaps as barriers V"to high levelsignals until the main discharge occurs at the window, the time requiredfor transfer of the discharge from the small gaps to the input window isllikewise determined by g and Q. The effectiveness of 'this phase ofoperation is usually rated in terms of the power `transmission throughthe element when the gaps are shorted. This transmission is considerablydecreased by the present construction; transmission thro-ugh a newdouble gap element is about -60 db as compared with -30 db of a standardiris and cone unit of the same Favorable broad band matching of TR tubesis accomplished by the use of one or more gap elements according to theinvention spaced at appropriate distances such as quarter wave lengthsapart from each other and a quarter wave length from the windows to forma multiple element band pass filter. Having in mind that band width isdetermined by the number and Q of 'the gap elements and windows, theimprovement presented in the above tabulation of characteristicproperties was obtained by means of a dual gap tuning element as shownin Fig. l, all post and elongate elements being identical and the postsbeing adjusted to equalize the gap spacing on either side of the tubulartransverse electrode to the value g given above.

The above described keep alive device which is particularly beneficialin combination with transversely tubular gap electrodes is used for thewell known purpose of providing electrons in the gap for rapid firingwhen the transmitted pulse begins. This is accomplished by means of adirect current glow discharge between the keep alive electrode and a gapand tuning electrode. According to the present invention this glowdischarge is located far enough from the tuning gap to prevent theexcessive attenuation of low level radio frequency signals which isknown as keep alive interaction. As compared with conventional keepalive electrode systems, namely the coaxial keep alive and the side armkeep alive, the system according to the invention combines the bestfeatures 4o-f these two previously suggested arrangements. The newsystem which is made possible by the hollow tuning element providesadequate space to prevent short circuiting and the gas discharge isremoved from the electromagnetic field in the transmission life.Therefore optimum effectiveness and long life are assured, as comtube.

6 pared with the conventional coaxial keep alive that suffers from spacelimitations leading to erosion of the 'tip eventually producing acontinuous metallic path `between the keep alive electrode 'and the coneor post resulting in a short circuit, and also as compared with thedetrimental properties of the conventional side arm -keep alive whichresult in poor leakage power control and ina discharge path located inthe electromagnetic field and therefore producing radio frequency noise.

The second keep alive described with reference to Fig. 4 considerablyincreases the reliability of a single TR Also, this second keep alivecan be pulsed to remove electrons from the gap and thereby to improvethe recovery time of the tube.

The modifications shown in Figs. 5, 6 `and 7 illustrate the adaptabilityof the system according to the invention. They show transverse elongate.principal gap elem/ents and keep alive elements according to theinvention, used separately or in combination. Figs. 5 and 6 indicate theuse of a single post electrode with Vtubular transverse electrode incombination with a double keep alive for the purpose mentioned above,whereas Fig. 7 shows the use of two posts electrodes on either side of atransversely elongate electrode which is in this instance solid.

As mentioned above, `the new gap electrode and keep alive structures areespecially beneficial with the dual window construction disclosed in theabove mentioned `application Ser. No. 657,585; as compared withco-nventional tubes made for equivalent purposes and power ratings, theyexhibit better uniformity in all characteristics, lower arc loss by afactor of two to one, lower insertion loss by a factor of two to one,and longer `tube life by a factor of two to one, at least partialelimination of sputtering and a more practical design from thestandpoint of reproducibility as well as flexibility.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

1. A discharge zgap rdevice comprising: a wave guide section, elongateelectrode means having a substantially linear outer surface regionextending transversely between and electrically connected directly toopposite wall portions of said guide section; and complementalsubstantially linear electrode means electrically connected directly toand extending from a third wall portion toward said elongate electrodemeans; whereby said electrode means form a discharge gap at pointslocated at a minimal distance from each other on the elongate andcomplemental electrode means, respectively.

2. A discharge gap device for ymounting within a wave guide, comprising:a pointed electrode mounted on and electrically connected directly to awall portion of the guide; and an elongate electrode electricallyconnected directly to and extending transversely between opposite wallportions of said guide, intersecting the axis of said pointed electrode,and having a linear surface portion freely exposed to said pointedelectrode; whereby the pointed electrode and the surface of thetransverselyelongate electrode form a discharge gap.

3. A discharge gap device for mounting within a wave guide, comprising:two pointed electrodes mounted in alignment on and electricallyconnected directly to opposite wall portions of the guide; and anelongate electrode electrically connected directly to and extendingtransversely between opposite wall portions of said guide andintersecting the common axis of said pointed electrodes; whereby thepointed electrodes and the transversely elongate electrode therebetweenform a double discharge gap.

4. A discharge gap device for mounting within a wave guide, comprising:pointed electrode means mounted on and electrically connected directlyto wall means of the guide; an elongate electrode means electricallyconnected directly `to and extending transversely between opposite ,Wallportions of said guide, intersecting the axis of the pointed electrodemeans; and conductor means extending transversely between andelectrically connected directly to wall means of the guide and saidelongate electrode means; whereby the electrode means form a dischargegap and the conductor means provide an electromagnetic inductance.

5. Device according to claim 4, wherein said conductor means includestwo rods whose axes substantially intersect the axis of said elongateelectrode means.

6. Device according to claim 4, wherein said conductor means includesbaflie plates whose plane substantially intersects the axis of saidelongate electrode means.

7. A discharge gap device for mounting within a wave guide, comprising:two pointed electrodes mounted in alignment on and electricallyconnected directly to opposite wall portions of the guide; an elongatethird electrode extending between said two pointed electrodestransversely between opposite wall portions of said guide, said thirdelectrode being electrically connected directly to at least one of saidopposite wall portions, intersecting the axis of the pointed electrodes;and metallic rod means extending between said opposite wall portions andsaid third electrode; whereby the electrodes form a double discharge gapand the rod means provide an electromagnetic inductance.

8. A discharge gap device for mounting within a wave guide, comprising:two pointed electrodes mounted in alignment on and electricallyconnected directly to opposite wall portions of the guide; an elongateelectrode electrically connected directly to and extending transverselybetween opposite wall portions of said guide and intersecting the axisof the pointed electrodes to form gaps therewith; and means for separateaxial adjustment of said pointed electrodes; whereby the gaps betweenthe elongate electrode and respective pointed electrodes can beseparately adjusted.

9. A discharge gap device comprising: two sections of two wave guidemeans mounted adjacent to each other with wall portions facing eachother; a tubular electrically conductive body extending transverselythrough both wave guide sections with sealed intersections of said wallportions, and having transverse perforations leading from the inside ofthe tubular electrode means into each one of the wave guide sections;whereby said tubular body constitutes a gap electrode in each guidesection and interconnects the sections.

10. Device according to claim 9 wherein each guide section contains twostud electrodes pointing towards said tubular body, forming a double gapin each wave guide section.

11. Device according to claim 9, further comprising auxiliary electrodemeans mounted within said tubular body and extending from one end of thebody towards one of said perforations.

12. Device according to claim 9 wherein said wall portions are joined.

13. A discharge gap device for mounting within a wave guide, comprising:pointed electrode means mounted on and electrically connected directlyto a wall portion of the guide; elongate hollow electrode means havingan exposed linear surface portion extending transversely of said guidebetween and electrically connected directly to two opposite wallportions thereof, intersecting the axis of said pointed electrode means,and having an opening opposite the apex region of the pointed electrodemeans; and auxiliary electrode means mounted to extend within saidelongate hollow electrode means from without the guide to said opening;whereby the electrode means form a discharge gap between the apex regionand the exposed surface portion, and the auxiliary electrode provides akeep alive means near the gap.

,14. A discharge gap device for mounting within a wave guide,comprising: pointed electrode means mounted on and electricallyconnected directly to a Wall portion of the guide; elongate hollowelectrodev means having an exposed linear surface portion freelyextending transversely of said guide between and electricallyr connecteddirectly to opposite wall portions thereof intersecting the axis of saidpointed electrode means, and having an opening opposite the apex regionof the pointed electrode means; auxiliary electrode means; insulatingmeans for suspending said auxiliary electrode means within said hollowelectrode means to extend therefrom without to said opening; and meansfor sealing the hollow electrode means around `the auxiliary electrodemeans; whereby the electrode means form a principal discharge gapbetween the apex region and the exposed surface portion, and theauxiliary electrode provides a keep alive means near the gap.

15. A resonant discharge gap device for mounting within a wave guide,comprising: two pointed electrodes mounted on and electrically connecteddirectly to opposite wall portions of the guide; a tubular electrodeextending between said two pointed electrodes transversely of said guidebetween and electrically connected directly to opposite wall portionsthereof intersecting the axes vof said pointed electrodes, said tubularelectrode having two perforations opposite the apex regions of said twopointed electrodes; and an auxiliary electrode mounted on insulatingsupport means such as to extend within said tubular electrode fromwithout the tubular electrode to said perforations; whereby the threeelectrodes form a double discharge gap, and the auxiliary electrodeprovides a keep alive means near the gap.

16. A resonant discharge gap device for mounting within a wave guide,comprising: two pointed electrodes mounted on and electrically connecteddirectly to opposite wall portions of the guide; a tubular elongateelectrode having a substantially linear outer surface region extendingbetween said two pointed electrodes transversely of said guide betweenand electrically connected directly to opposite wall portions thereof,intersecting the axes of said pointed electrodes and having a linearportion freely exposed to said pointed electrode, said tubular electrodehaving two perforations opposite the apex regions of said two pointedelectrodes; and two auxiliary electrodes mounted on insulating supportmeans such as to extend within said tubular electrode from withouteither end thereof towards said perforations; whereby the tubular andpointed electrodes form a double discharge gap, and the auxiliaryelectrodes provide keep alive means near the gap.

17. A discharge gap device for mounting within a wave guide, comprising:an elongate hollow electrically conductive `body having an exposed outerlinear surface portion and being adapted for mounting transverselybetween and electrically connected directly to two opposite wallportions extending through at least one wall portion of the guide, andin said surface portion a perforation transversely through a wallportion of the hollow body and leading into the guide; and metallic rodmeans extending from without said wall portion into said hollow body andterminating near said perforation; whereby the hollow body provides agap electrode and the rod means provide a keep alive device for a gapnear said perforation.

18. In a discharge gap device as one of a plurality of gap electrodesfor mounting within a wave guide: an elongate hollow electricallyconductive body having an exposed surface portion arranged for extendinglinearly between an electrically connected directly to wall portions andthrough at least one wall portion off the guide and having transverselyto its wall a perforation leading into the guide; metallic rod meansextending within said hollow body from an end thereof near to saidopening; and electrical insulator means for supporting the metallic rodmeans within the hollow body; whereby the body provides a gap electrodeand the rod provides keep alive means therewithin at the perforation.

19. In a discharge gap device as one of a plurality of gap electrodes-for mounting within a wave guide: a 'tubular electrically conductivebody open at both ends, arranged for extending transversely of the guidebetween and through opposite wall portions of the guide, said body beingelectrically connected directly to `at least one of said opposite wallportions and having a transverse perforation leading into the guide; aconductor leading into the tubular body through one of its ends and terminating near said perforation; and supporting means for said conductorextending within said tubular body and including an insulating sealingbead; whereby the tubular body provides a gap electrode and theconductor provides keep 'alive means therewithin at the perforation.

20. In a discharge gap device as one of a plurality of gap electrodesfor mounting within a wave guide: a tubular electrically conductive bodyopen at both ends, arranged for extending transversely of the guidebetween and through opposite wall portions of the guide, said body beingelectrically connected directly to at least one of said opposite wallportions and having two perforations leading radially into the guide; aconductor leading into the tubular body through one of its ends andterminating near said perforations; and supporting means for saidconductor extending within said tubular body and including a sealingbead; whereby the tubular body provides an intermediate electrode for adouble gap near said two perforations and the conductor provides keepalive means therewithin at the perforations.

21. In a discharge gap device as one of a plurality of gap electrodesfor mounting within a wave guide: a tubular electrically conductive bodyproviding an elongate electrode having a substantially linear outersurface region, said body being open at both ends and extendingtransversely of said guide between and through opposite wall portions ofthe guide said body being electrically connected directly to at leastone of said opposite wall portions and having a transverse perforationleading into the guide; two conductors extending into the tubular bodyone through each of its ends and sep arately terminating near saidperforation; and support- Iing means for said conductors extendingwithin said tubular body and including sealing beads one for cachconductor near its end of Ithe tubular body and supporting -beads nearythe perforation; whereby the tubular body provides a gapelectrode andthe two conductors provide keep alive means therewithin at ltheperforation.

22. In a discharge gap device as one of a plurality of gap electrodesfor mounting within a wave guide: a tubular electrically conductive bodyproviding an elongate electrode having a substantially linear outersurface region, said body being open at both ends and extendingtransversely of said guide between and through opposite wall portions ofthe guide said body being electrically connected directly to at leastone of said opposite 'wall portions and having two diametricallyopposite transverse perforations leading into the guide; two conductorsextending into the tubular body one through each of its ends andseparately terminating near said peroration; and supporting means forsaid conductors extending within said tubular body and including sealingbeads one for each conductor near its end of the tubular body andsupporting beads near the perforations; whereby the tubular bodyprovides a gap electrode and the two conductors provide keep alive meanstherewithin at the perforations.

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